1 

To: Brian Shrager, EPA/SPPD 

From: Amanda Singleton, ERG 

Date: August 2, 2010 

Re: Minutes of Oil and Gas Industry Meeting – July 21st, 2010 

Meeting Attendees 

Clay Freeber, Chevron 

Charlie Bennett, Marathon 

Glenn England, Environ 

Douglas VanPelt, Exxon Mobil 

Norm Morrow, Fresh Air Consulting 

Matt Todd, API 

Hector Ayala, Exxon Mobil 

Jack McClure, JLM Group 

Bob Hermanson, BP America 

Matt Hodges, Valero Energy 

Jan Laughlin, Conoco Phillips 

Shari Keller, Shell 

David Friedman, NPRA 

Bob Wayland, Mary Johnson, Brian Shrager, Brenda Shine, USEPA 

Amanda Singleton, ERG 

Meeting Themes 

 Both gaseous fuel categories should have a work practice standard 

 Optimizing combustion, instead of minimizing CO levels, should be the goal of tune-up work practice 

standards 

 Achievability of emission limits and demonstration of controls on gas-fired units 

 Facility-wide energy audit is not justified 

Emissions from Gas 1 and Gas 2 Subcategories 

Glenn England plotted the CO emissions from Gas 1 and Gas 2 boilers and concluded that emissions of CO from 

these two gas subcategories are similar with the exception of some process gas numbers that appear to either be 

outliers or representative of where a unit is operating on a downcycle mode or at increased levels of excess air. 

Mr. England also plotted emissions of organic HAP from various gaseous fuel blends and operating conditions at 

refineries and he indicated that emissions of organic HAPs are near detection limits except under certain operating 

conditions, such as startup and shutdown, or lower loads. Fuel characteristics did not affect emissions of organic 

HAP. 

Mr. England presented that many gas fuels do not have any significant quantities of Hg or chlorine present in the 

fuel that would result in emissions of Hg or HCl emissions. He requested that if limits were to be established for 
 

 2 

gaseous fuels that a fuel analysis based standard, in lieu of an outlet stack test standard, would be the more 

appropriate method of limiting emissions of these two pollutants. 

Given the similarity of the emissions profiles from gas 1 and gas 2 subcategories Mr. England requested that both 

gaseous fuel categories be subject to work practice standards. 

Combustion Curves and Relationship between CO and NOx 

Hector Ayala presented a combustion curve that plotted CO and NOx emissions against excess air levels. The curve 

showed that very low CO emissions require a level of excess air that results in elevated NOx emissions and lower 

than optimal combustion efficiency. A side effect of very low CO limits for gas units would be higher emissions of 

NOx and a lower the efficiency of the boiler, thereby increasing CO2 emissions and emissions of other HAP as a 

result of increased fuel use. 

Instead of having the goal of the tune-up be to minimize CO emissions, the goal of the tune-up should be to tune the 

boiler to the appropriate maximum operating efficiency range, which is typically between 2 and 4 percent oxygen 

for units at petroleum refineries. It was noted that the optimal oxygen levels will vary depending on the unit design, 

and he added that there is typically a margin of error on how much excess air is required to achieve maximum 

operating efficiency in order to avoid operational safety hazards at the boiler. 

Achievability of Emission Limits/Demonstrated Control Technologies at Gas Fired Units 

Mr. England presented a flow diagram of a natural draft process heater and the sequence of anticipated controls 

necessary to meet the alternative emission limits proposed for gas-fired combustion units. He noted that the retrofit 

factors used for refinery units were too low considering the space constraints at refineries. Mr. England also noted 

that the series of additional controls cause significant pressure drop which will prevent the use of natural draft 

process heaters. In these cases the natural draft units would need to be replaced with forced draft units and the cost 

of this replacement was not considered in the impacts analysis. 

Mr. England also noted that there are not any gas-fired units in operation that have installed the full suite of 

controls. Given the low concentrations of pollutants emitted from gas units, there is no guarantee that these controls 

can achieve the necessary efficiencies to meet the alternative proposed emission limits. 

Facility-wide Energy Audit is not Justified 

Norm Morrow presented on the industry’s concerns with energy audits contained in the proposal: 

 First, the analysis assumes a one percent improvement in efficiency as a result of the audit. Many industries 

have already undergone extensive energy management programs and as a result this improvement is 

optimistic. 

 Second, the cost of the audit is closer to $100,000 per facility for plants in the refinery and petrochemicals 

sectors, which is double the costs of the audit assumed in EPA’s proposal. 

 Third, the audit expands beyond the source category. Industry will be providing detailed comments about the 

legal and precedent issues of incorporating a facility-wide audit to a source category MACT program. 

 Finally, the industry disagrees with the EnergySTAR energy management program requirement. 

Industry representatives noted that they would be providing EPA with detailed written comments and data to 

support their claims. 

Attachment 1: Slides presented during meeting. 
1

Gas Fuels: HAPs Are Below or Near Detection 

Limits for Wide Range of Fuels, Normal Conditions

Source: England et al., Chemosphere 2001

Pilot-scale
2

ICR Data for Gas Fuels (not metal furnaces)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 2 4 6 8 1 0 1 2 1 4 1 6 1 8 CO, ppm @ 3%O2

Gas 1 Natural Gas Refinery Gas

Gas 2 Gas 2 w/o Petroluem Coke Coke Oven Gas

Coke Oven Gas w/o Petroleum Coke Landfill Gas Vent Gas for Air Pollution Control

Biogas/Natural gas Biogas Process Gas

Process Gas (excl outliers) Petrochemical Process Gas Natural Gas/Petrochemical Process Gas

Natural Gas/Process Gas Blast Furnace Gas

Gas1 NM Gas 2
3

-5 0

0

5 0

100

150

200

0 2 4 6 8 1 0 1 2 1 4 1 6 1 8 CO, ppm @ 3% O2

Gas 1 Natural Gas Refinery Gas

Gas 2 Gas 2 w/o Petroluem Coke Coke Oven Gas

Coke Oven Gas w/o Petroleum Coke Landfill Gas Vent Gas for Air Pollution Control

Biogas/Natural gas Biogas Process Gas

Process Gas (excl outliers) Petrochemical Process Gas Natural Gas/Petrochemical Process Gas

Natural Gas/Process Gas

Gas1 NM Gas 2

symbols = mean

Error bars = 95% confidence 

intervals

Process gas (including

outliers,12 data points 

from 4 units at 2 

facilities).

Process gas (excluding

outliers, 227 data 

points remaining.)

Process/Petrochemical gas fuels have 

low CO emissions

CO Levels Are Similar Among HC Fuels

Source: EPA ICR Database,Version 5)
4

A work practice for gas fuels is appropriate

• Organic HAP emissions from gas fuels are below or near detection 

limits over a wide range of normal, good combustion conditions

• Emissions from natural gas, refinery gas, petrochemical and process gas 

fuels are similar on a Btu basis

• Exceptions are system rather than fuel related

• Good combustion achieved via a work practice standard optimizes 

systems for lowest emissions and energy consumption commensurate 

with safe operation

• Gas fuels with no significant fuel-based HAP precursors (e.g., Cl, 

Hg) have no significant metallic/inorganic HAP emissions

• EPA could establish de minimus standards for fuel-based HAP 

precursors
5

• Maintaining low CO limits for gas-fired units will lead to non-optimum 

operation/efficiency and will increase other pollutants

• CO Limit will have an adverse effect on NOx emissions

• CO Limit will reduce energy efficiency and subsequently increase CO2

emissions

• Requiring 1ppm CO is Technically Infeasible while maintaining NOx 

emissions targets, and operating efficiently

• Low CO emissions are favored by high temperature, high O2, rapid mixing 

and long residence time

• NOx is an undesirable byproduct favored by high temperatures, high O2, 

and rapid mixing (via “thermal”, “prompt” and “fuel” NOx mechanisms) 

• Emissions control is a trade-off between NOx and CO

• Minimum CO occurs at maximum NOx generation

• Leads to higher NOx formation, which is a precursor to smog

Impact of CO Limit on Other Emissions
6

CO, NOx as a Function of O2

0 2 4 6 8 1 0 1 2 1 4

Excess Oxygen, %v

CO

NOx

Thermal Efficiency Unsafe: Flame stability and explosion hazard

Normal Operating 

Envelope for maximum 

efficiency limited by CO

Maximum 

thermal 

efficiency

Typical CO limit 

for boiler tuning

Unsafe

Flammability 

and/or flame 

Safety blowoff limits

Margin
7

• Attempts to Meet CO Limit will Reduce Energy Efficiency

• Reducing CO to extremely low levels will require an increase in excess air 

levels which will reduce efficiency

• This will increase the amount of fuel that must be fired, therefore increasing 

the total mass of other pollutants (HAPs, NOx, SOx, PM, etc)

• Efforts to maximize efficiency and NOx reduction have been 

accomplished by reducing excess air levels until the point where CO 

emissions begin to increase

• Operation at levels where CO ranges from 100 - 400ppm provides the 

most efficient balance between stack heat losses and lost potential 

energy from incomplete CO oxidation

• Thermal efficiency is close to optimized at current NOx, CO levels (see 

graph)

Impact of CO Limit on Energy Efficiency
8

• During SSM periods, boilers and process heaters operate at offdesign conditions with low firing rates and high excess air levels

• At these low loads, mixing energy of the fuel and air in the combustion 

process is much lower. CO will increase during this operation

• For multiple-burner boilers NFPA code does not allow airflow < 25%

• Good operating practices require equipment be gradually warmed-up to 

operating temperature in order to prevent thermal damage in mechanical 

components

• OEMs give guidance on heat-up rates and require it for equipment warranty

• Limit life of units due to a need to increase start-up rate (and stresses)

• Attempting to meet 1ppm CO during SSM periods would discourage 

proper start-up/shutdown of equipment – i.e. operators would quickly 

ramp up boiler to minimize off-design operation. This is not desirable.

• Majority of combustion incidents (near-misses, explosions) have occurred 

during SSM periods

Impact of CO Limit on Safe Operations
9

• Industry typically operates 

fired equipment with 

margin on excess air (O2)

• To better handle rapid 

boiler steam load 

changes when 

demanded by users and 

when impacted by 

inclement weather

• Important for maintaining 

emissions and 

combustion stability

Operating with Safety Margin
10

CO vs. HAP During Constant Load Tests

All (including metal furnaces)

0

50

100

150

200

250

300

350

400

450

0.01 0.1 1 10 100 1000 10000

CO, ppm @ 3% O2

THC, ppm @ 3% O2

0

10

20

30

40

50

60

70

80

90

100

Formaldehyde, ppm @ 3% O2

THC NM (Gas 1) THC NM (Gas 2) THC M (Gas 1) Formaldehyde NM (Gas 1) Formaldehyde NM (Gas 2) Formaldehyde M (Gas 1)

Outliers

Source: EPA ICR database, version 5
11

Gas-Fired Process Heater (Natural Draft)

• Natural draft

• No forced draft or induced draft fans

• Combustion air induced by stack gas 

buoyancy and fuel pressure

• Wide variety of furnace and burner 

configurations

• Designed for specific heat duty

• Furnace geometry and size

• Bottom-fired, side-fired, down-fired

• ~4-100+ individual burners

• Exhaust gas temperature ~500-700 F

• 1000’s of such units in petroleum 

refineries & petrochemical plants
12

Process Heater (Natural Draft) on MACT

• CO: combustion controls & oxidation 

catalyst

• Hg, D/F & PM: ACI + FF

• HCl: packed bed wet gas scrubber

• Conversion to balanced draft required 

to offset pressure drop

Technically infeasible because:

 Retrofit infeasible, replacement likely

 Unproven emissions reduction at low inlet 

concentrations

 Outlet concentrations below detection limits

 Increased energy, water consumption
13

Retrofit Constraints
14

Retrofit Constraints